1. Field of the Invention
The present invention relates to a photoacoustic measurement apparatus, that is, an apparatus for irradiating a subject, such as biological tissue, with light and performing processing for imaging the subject on the basis of a photoacoustic wave generated with light irradiation, or the like.
Further, the invention relates to a probe that is used in this kind of photoacoustic measurement apparatus.
2. Description of the Related Art
For some time, a photoacoustic imaging apparatus, which images the inside of a living body by using a photo-acoustic effect, has been known, as disclosed in, for example, JP2005-21380A and A High-Speed Photoacoustic Tomography System based on a Commercial Ultrasound and a Custom Transducer Array, Xueding Wang, Jonathan Cannata, Derek DeBusschere, Changhong Hu, J. Brian Fowlkes, and Paul Carson, Proc. SPIE Vol. 7564, 756424 (Feb. 23, 2010). In the photoacoustic imaging apparatus, the inside of the living body is irradiated with pulsed light such as a pulsed laser beam. In the inside of the living body that has been irradiated with the pulsed light, the volume of biological tissue having absorbed the energy of the pulsed light is expanded by heat and the biological tissue generates a photoacoustic wave (acoustic signal). Accordingly, the photoacoustic wave is detected with an ultrasonic probe or the like, and the visible image of the inside of the living body can be formed on the basis of a detected signal.
In the other hand, an ultrasonic imaging apparatus using an ultrasonic probe also is well-known as disclosed in WO2009/069379A and JP2011-10827A. This kind of ultrasonic probe includes an ultrasonic transducer at an end thereof. In many cases, the ultrasonic probe includes a backing material, a piezoelectric body, electrodes between which the piezoelectric body is interposed, an acoustic matching layer, an acoustic lens, and the like. In the ultrasonic imaging apparatus, an ultrasonic wave is applied to a subject, such as the human body, from the ultrasonic transducer and an ultrasonic wave reflected from the subject is received by the ultrasonic transducer. Further, a detection signal of the reflected ultrasonic wave is electrically processed, so that an ultrasonic image is obtained.
Meanwhile, in this specification, an elastic wave generated from the probe is referred to as an ultrasonic wave and an elastic wave generated due to a photo-acoustic effect is referred to as a photoacoustic wave.
Since the above-mentioned ultrasonic probe can detect not only an ultrasonic wave but also a photoacoustic wave, the ultrasonic probe is also widely used in photoacoustic measurement apparatuses. That is, in this kind of apparatus, a light irradiating unit, which irradiates a subject with light, is added to the ultrasonic probe and a photoacoustic wave, which is generated from the subject receiving light from the light irradiating unit, is detected by an ultrasonic transducer of the ultrasonic probe.